Analysis of inherited tendency of fruit characteristics in F1 group of reciprocal crossing between ‘Chuanzhihong’ and ‘Saimaiti’ in apricots

Abstract：【Objective】The study was undertaken to explore the genetic tendency of main traits in F1 generation of apricot, so as to provide a basis for the prediction of parental selection and offspring traits in apricot breeding.【Methods】In this experiment, the cross combinations were set as‘Saimaiti’בChuanzhihong’and‘Chuanzhihong’בSaimaiti’. The‘Saimaiti’בChuanzhihong’was the positive cross combination including 213 strains, while‘Chuanzhihong’בSaimaiti’was the negative cross combination including 110 strains. They were crossed in 2006 and planted in 2007, and fruit traits were investigated in 2018 and 2019. In order to examine the fruit shape, fruit surface color, single fruit weight, fruit hardness and soluble solid content of the reciprocal cross combination for‘Saimaiti’and ‘Chuanzhihong’, ten fruits were collected from each hybrid. The fruit weight was measured with an electronic balance and the vertical, horizontal and side diameters of the fruit were measured with a vernier caliper. The content of soluble solids was determined by a digital Brix spindke. Fruit hardness wasmeasured with an Agrosta2019 fruit texture detector. The test was made after peeling, the penetration depth was 8.5mm, the penetration speed was 15mm/s, and the selected probe area was 1cm2 . The data of this experiment were collated by Excel 2019, statically analyzed by SPSS 19, plotted by Origin 2015 and calculated by genetic transmission force and coefficient of variation.【Results】The frequency distribution of fruit weight tended to be normal distribution. The average single fruit weight of the progeny of the reciprocal cross combinations was lower than the low parent. The average fruit weight of positive combinations was lower than that of low parent, being 92.94% and 84.72%, respectively. The negative cross was 96.08% and 82.85%, respectively. The tendency toward small heredity was manifested. The variation coefficients of fruit weight in positive combinations were 30.38% and 35.48% but those in negative cross combinations were 25.34% and 24.14%. The degree of variation was significant. In each combination, there were no superhigh parent lines in longitudinal, transverse and side diameters in the progeny of the reciprocal cross combinations, and they were generally lower than the low affinity value. The coefficients of variation of all groups were consistently lower, and the genetic transmission was higher. The results showed that the heredity of longitudinal diameter, transverse diameter and lateral diameter of fruit was less affected by environmental factors. The fruit shapes of‘Chuanzhihong’and ‘Saimaiti’were oval. Meanwhile, the oval, oblate, irregular, heart-shaped and round-shaped separation occurred in the reciprocal cross combinations. The oval strains of each combination accounted for the highest proportion, reaching about 90%. The tendency was toward oval heredity. The fruit color of‘Chuanzhihong’was red, and the fruit color of‘Saimaiti’was colorless. In the progeny of reciprocal cross combinations, the pink, orange-red, red color and colorless were found. In 2018, among the offsprings of orthogonal combination, the proportion of plants colorless on fruit surface was 24.46%, and the proportion of colorful blush color strains was 75.54%. In 2019, the proportion of colorless in the offsprings of orthogonal combinations was 41.87%, colorful blush color accounted for 58.13%. In 2018, the proportion of colorless was 37.25%. The proportion of colorful blush color strains was 62.75%. In 2019, the proportion of colorless was 33.33%, and the proportion of colorful blush color was 66.67%. The colorful blush color of the reciprocal cross offsprings occupied a large proportion. After the card square test, the result was in a ratio of 1∶3, which showed that the colorful blush color of apricot fruit was dominant, compared with colorless. The result also showed that, the contents of soluble solids in the progeny of‘Chuanzhihong’and‘Saimaiti’were continuously variable, and normally distributed. The soluble solids content of apricot fruit was a quantitative trait controlled by multiple genes. The mean value of soluble solids in the progenies of the reciprocal cross combinations was lower than the mean value of affinity. The proportions higher than the high parent in orthogonal cross combinations were 10.87% and 2.96%, and the proportions lower than low parent were 10.87% and 2.96%, respectively. The proportions higher than the high parent in negative cross combinations were 15.69% and 4.76%，and the proportions lower than low parent were 31.38% and 9.52% . The heritability of each combination was 91.09% , 96.99% , 94.91% and 96.72% , respectively. The variation coefficients of each combination were 15.73%, 14.25%, 12.31% and 11.51%, respectively. The mean fruit hardness of the 18-year and 19-year progenies of‘Chuanzhihong’and‘Saimaiti’were lower than the median of parents. Most of them were lower than low parent. The proportions of fruit hardness lower than low parent of positive cross combinations were 75% and 85.22%. In the negative cross, the proportions of fruit hardness lower than low parent were 67.65% and 75.24%. It showed an obvious tendency toward low inheritance. The variation coefficients of reciprocal cross combinations were 34.12%, 26.37%, 18.65% and 28.64%, respectively. In two years of investigation, the heritability of each combination was 61.37% , 66.63% ,68.84% and 71.62%, respectively. The fruit flavor of‘Chuanzhihong’was mainly sweet and sour, and the fruit flavor of‘Saimaiti’was mainly sweet. In two years, strains tasted sweet and sour had the largest number in all the combinations, surpassing 70%. Minute quantity strains tasting sweet and/or sour were found in all the combinations, so the fruit flavor showed a genetic tendency to sour taste.【Conclusion】Fruit weight, vertical diameter, lateral width and ventral width almost formed by additive effect in the reciprocal crossed population. The additive effect of orthogonal cross combination was similar to negative cross combination, and they were disintegrated completely. The additive effect of soluble solids content in all the reciprocal cross combinations was disintegrated, but new additive effect formed in the progeny, and there were new strains that were higher than the high parent in the progeny.